Introduction to Communications Qilian Liang Department of Electrical Engineering University of Texas at Arlington liang@uta.edu _________________ Adapted from Stanford University EE359 by Andrea Goldsmith Adapted from Stanford University EE104 by Prof. Andrea Goldsmith

Communication Systems Provide for electronic exchange of multimedia data Voice, data, video, music, email, web pages, etc. Communication Systems Today Radio and TV broadcasting Public Switched Telephone Network (voice,fax,modem) Cellular Phones Computer networks (LANs, WANs, and the Internet) Satellite systems (pagers, voice/data, movie broadcasts) Bluetooth

Communication System Block Diagram Text Images Video Source Encoder Transmitter Source Decoder Channel Receiver Source encoder converts message into message signal or bits. Transmitter converts message signal or bits into format appropriate for channel transmission (analog/digital signal). Channel introduces distortion, noise, and interference. Receiver decodes received signal back to message signal. Source decoder decodes message signal back into original message.

PSTN Design Local exchange Circuit switched network tailored for voice Local Switching Office (Exchange) Local Switching Office (Exchange) Long Distance Lines (Fiber) Fax Modem Local Line (Twisted Pair) Local exchange Handles local calls Routes long distance calls over high-speed lines Circuit switched network tailored for voice Faxes and modems modulate data for voice channel DSL uses advanced modulation to get 1.5 Mbps

Wireless History Ancient Systems: Smoke Signals, Carrier Pigeons, … Radio invented in the 1880s by Marconi Many sophisticated military radio systems were developed during and after WW2 Cellular has enjoyed exponential growth since 1988, with almost 5 billion users worldwide today Ignited the wireless revolution Voice, data, and multimedia ubiquitous Use in third world countries growing rapidly Wifi also enjoying tremendous success and growth Wide area networks (e.g. Wimax) and short-range systems other than Bluetooth (e.g. UWB) less successful

Current Wireless Systems Cellular Systems Wireless LANs Convergence of Cellular and WiFi WiGig and Wireless HD Satellite Systems Zigbee radios

Cellular Systems: Reuse channels to maximize capacity Geographic region divided into cells Frequency/timeslots/codes reused at spatially-separated locations. Co-channel interference between same color cells (reuse 1 common now). Base stations/MTSOs coordinate handoff and control functions Shrinking cell size increases capacity, as well as networking burden BASE STATION MTSO

Cell Phone Backbone Network San Francisco BS BS New York MTSO MTSO PSTN BS Internet Internet Internet

Challenges Network Challenges Device Challenges Scarce spectrum Demanding/diverse applications Reliability Ubiquitous coverage Seamless indoor/outdoor operation Device Challenges Size, Power, Cost Multiple Antennas in Silicon Multiradio Integration Coexistance Cellular Apps Processor BT Media GPS WLAN Wimax DVB-H FM/XM

Software-Defined (SD) Radio: Is this the solution to the device challenges? BT A/D FM/XM Cellular GPS A/D DVB-H DSP Apps Processor A/D WLAN Media Processor Wimax A/D Wideband antennas and A/Ds span BW of desired signals DSP programmed to process desired signal: no specialized HW Today, this is not cost, size, or power efficient Compressed sensing may be a solution for sparse signals

LTE backbone is the Internet Cellular Phones Burden for this performance is on the backbone network Everything wireless in one device BS Phone System San Francisco Paris Nth-Gen Cellular Internet LTE backbone is the Internet Much better performance and reliability than today - Gbps rates, low latency, 99% coverage indoors and out

4G/LTE Cellular Much higher data rates than 3G (50-100 Mbps) 3G systems has 384 Kbps peak rates Greater spectral efficiency (bits/s/Hz) Through MIMO, adaptive techniques, “ICIC” Flexible use of up to 100 MHz of spectrum 20 MHz spectrum allocation common Low packet latency (<5ms). Reduced cost-per-bit Support for multimedia All IP network

Careful what you wish for… Exponential Mobile Data Growth Leading to massive spectrum deficit Source: FCC Source: Unstrung Pyramid Research 2010 Growth in mobile data, massive spectrum deficit and stagnant revenues require technical and political breakthroughs for ongoing success of cellular

Rethinking “Cells” in Cellular How should cellular systems be designed? Coop MIMO Femto Relay Will gains in practice be big or incremental; in capacity or coverage? DAS Traditional cellular design “interference-limited” MIMO/multiuser detection can remove interference Cooperating BSs form a MIMO array: what is a cell? Relays change cell shape and boundaries Distributed antennas move BS towards cell boundary Femtocells create a cell within a cell Mobile cooperation via relays, virtual MIMO, network coding.

10x CAPACITY Improvement The Future Cellular Network: Hierarchical Architecture 10x Lower COST/Mbps 10x CAPACITY Improvement Near 100% COVERAGE (more with WiFi Offload) Today’s architecture 3M Macrocells serving 5 billion users Anticipated 1M small cells per year MACRO: solving initial coverage issue, existing network PICO: solving street, enterprise & home coverage/capacity issue Macrocell Picocell Femtocell Future systems require Self-Organization (SON) and WiFi Offload

SON Premise and Architecture Mobile Gateway Or Cloud Node Installation Initial Measurements Self Optimization Self Healing Self Configuration Measurement SON Server SoN Server IP Network X2 X2 SW Agent X2 X2 SON is part of 3GPP/LTE standard Small cell BS Macrocell BS

Green” Cellular Networks Pico/Femto How should cellular systems be redesigned for minimum energy? Coop MIMO Relay DAS Research indicates that significant savings is possible Minimize energy at both the mobile and base station via New Infrastuctures: cell size, BS placement, DAS, Picos, relays New Protocols: Cell Zooming, Coop MIMO, RRM, Scheduling, Sleeping, Relaying Low-Power (Green) Radios: Radio Architectures, Modulation, coding, MIMO

Future Wireless Networks Ubiquitous Communication Among People and Devices Next-generation Cellular Wireless Internet Access Wireless Multimedia Sensor Networks Smart Homes/Spaces Automated Highways In-Body Networks All this and more …

Wifi Networks Multimedia Everywhere, Without Wires Streaming video Gbps data rates High reliability Coverage in every room Wireless HDTV and Gaming

Wireless Local Area Networks (WLANs) 1011 01011011 0101 Internet Access Point WLANs connect “local” computers (100m range) Breaks data into packets Channel access is shared (random access) Backbone Internet provides best-effort service Poor performance in some apps (e.g. video)

Wireless LAN Standards 802.11b (Old – 1990s) Standard for 2.4GHz ISM band (80 MHz) Direct sequence spread spectrum (DSSS) Speeds of 11 Mbps, approx. 500 ft range 802.11a/g (Middle Age– mid-late 1990s) Standard for 5GHz band (300 MHz)/also 2.4GHz OFDM in 20 MHz with adaptive rate/codes Speeds of 54 Mbps, approx. 100-200 ft range 802.11n Standard in 2.4 GHz and 5 GHz band Adaptive OFDM /MIMO in 20/40 MHz (2-4 antennas) Speeds up to 600Mbps, approx. 200 ft range Other advances in packetization, antenna use, etc. Many WLAN cards have all 3 (a/b/g) What’s next? 802.11ac/ad

Convergence of Cellular and WiFi LTE.11 Seamless handoff between networks Load-balancing of air interface and backbone Carrier-grade performance on both networks

Software-Defined Network Virtualization Wireless Network Virtualization Layer Network virtualization combines hardware and software network resources and functionality into a single, software-based virtual network

WiGig and Wireless HD New standards operating in 60 GHz band Data rates of 7-25 Gbps Bandwidth of around 10 GHz (unregulated) Range of around 10m (can be extended) Uses/extends 802.11 MAC Layer Applications include PC peripherals and displays for HDTVs, monitors & projectors

Satellite Systems Cover very large areas Different orbit heights GEOs (39000 Km) versus LEOs (2000 Km) Optimized for one-way transmission Radio (XM, Sirius) and movie (SatTV, DVB/S) broadcasts Most two-way systems struggling or bankrupt Global Positioning System (GPS) use growing Satellite signals used to pinpoint location Popular in cell phones, PDAs, and navigation devices

IEEE 802.15.4/ZigBee Radios Low-Rate WPAN Data rates of 20, 40, 250 Kbps Support for large mesh networking or star clusters Support for low latency devices CSMA-CA channel access Very low power consumption Frequency of operation in ISM bands Focus is primarily on low power sensor networks

Tradeoffs 802.11n 3G Rate 802.11g/a Power 802.11b UWB Bluetooth ZigBee Range

Scarce Wireless Spectrum $$$ and Expensive

Spectrum Regulation Spectrum a scarce public resource, hence allocated Spectral allocation in US controlled by FCC (commercial) or OSM (defense) FCC auctions spectral blocks for set applications. Some spectrum set aside for universal use Worldwide spectrum controlled by ITU-R Regulation is a necessary evil. Innovations in regulation being considered worldwide in multiple cognitive radio paradigms

Spectral Reuse Due to its scarcity, spectrum is reused BS In licensed bands and unlicensed bands Wifi, BT, UWB,… Cellular, Wimax Reuse introduces interference

Cognitive Radios Cognitive radios can support new wireless users in existing crowded spectrum Without degrading performance of existing users Utilize advanced communication and signal processing techniques Coupled with novel spectrum allocation policies Technology could Revolutionize the way spectrum is allocated worldwide Provide sufficient bandwidth to support higher quality and higher data rate products and services

Cognitive Radio Paradigms Underlay Cognitive radios constrained to cause minimal interference to noncognitive radios Interweave Cognitive radios find and exploit spectral holes to avoid interfering with noncognitive radios Overlay Cognitive radios overhear and enhance noncognitive radio transmissions Knowledge and Complexity

Standards Interacting systems require standardization Companies want their systems adopted as standard Alternatively try for de-facto standards Standards determined by TIA/CTIA in US IEEE standards often adopted Process fraught with inefficiencies and conflicts Worldwide standards determined by ITU-T In Europe, ETSI is equivalent of IEEE Standards for current systems are summarized in Appendix D.

Emerging Systems* Cognitive radio networks Ad hoc/mesh wireless networks Sensor networks Distributed control networks The smart grid Biomedical networks *Can have a bonus lecture on this topic late in the quarter if there is interest

Ad-Hoc/Mesh Networks ce Outdoor Mesh Indoor Mesh

Design Issues Ad-hoc networks provide a flexible network infrastructure for many emerging applications. The capacity of such networks is generally unknown. Transmission, access, and routing strategies for ad-hoc networks are generally ad-hoc. Crosslayer design critical and very challenging. Energy constraints impose interesting design tradeoffs for communication and networking.

Wireless Sensor Networks Data Collection and Distributed Control Smart homes/buildings Smart structures Search and rescue Homeland security Event detection Battlefield surveillance Energy (transmit and processing) is the driving constraint Data flows to centralized location (joint compression) Low per-node rates but tens to thousands of nodes Intelligence is in the network rather than in the devices

Energy-Constrained Nodes Each node can only send a finite number of bits. Transmit energy minimized by maximizing bit time Circuit energy consumption increases with bit time Introduces a delay versus energy tradeoff for each bit Short-range networks must consider transmit, circuit, and processing energy. Sophisticated techniques not necessarily energy-efficient. Sleep modes save energy but complicate networking. Changes everything about the network design: Bit allocation must be optimized across all protocols. Delay vs. throughput vs. node/network lifetime tradeoffs. Optimization of node cooperation. All the sophisticated high-performance communication techniques developed since WW2 may need to be thrown out the window. By cooperating, nodes can save energy

Distributed Control over Wireless Automated Vehicles - Cars - Airplanes/UAVs - Insect flyers Interdisciplinary design approach Control requires fast, accurate, and reliable feedback. Wireless networks introduce delay and loss Need reliable networks and robust controllers Mostly open problems : Many design challenges

The Smart Grid: Fusion of Sensing, Control, Communications carbonmetrics.eu

Applications in Health, Biomedicine and Neuroscience Neuro/Bioscience EKG signal reception/modeling Brain information theory Nerve network (re)configuration Implants to monitor/generate signals In-brain sensor networks Body-Area Networks Doctor-on-a-chip Wireless Network Recovery from Nerve Damage